/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.consensus.common;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

public class Utils {
    private static final Logger logger = LoggerFactory.getLogger(Utils.class);

    public static List<Path> listAllRegularFilesRecursively(File rootDir) {
        List<Path> allFiles = new ArrayList<>();
        try {
            Files.walkFileTree(
                    rootDir.toPath(),
                    new FileVisitor<Path>() {
                        @Override
                        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                                throws IOException {
                            return FileVisitResult.CONTINUE;
                        }

                        @Override
                        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
                                throws IOException {
                            if (attrs.isRegularFile()) {
                                allFiles.add(file);
                            }
                            return FileVisitResult.CONTINUE;
                        }

                        @Override
                        public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
                            logger.info("visit file {} failed due to {}", file.toAbsolutePath(), exc);
                            return FileVisitResult.TERMINATE;
                        }

                        @Override
                        public FileVisitResult postVisitDirectory(Path dir, IOException exc)
                                throws IOException {
                            return FileVisitResult.CONTINUE;
                        }
                    });
        } catch (IOException ioException) {
            logger.error("IOException occurred during listing snapshot directory: ", ioException);
            return Collections.emptyList();
        }
        return allFiles;
    }

    public static class MemorizedFileSizeCalc {
        private List<Path> memorized;
        private final File rootDir;
        private long totalSize;

        public MemorizedFileSizeCalc(File rootDir) {
            this.memorized = Collections.emptyList();
            this.rootDir = rootDir;
            this.totalSize = 0;
        }

        public synchronized long getTotalFolderSize() {
            final List<Path> latest = listAllRegularFilesRecursively(rootDir);

            final List<Path> incremental =
                    latest.stream().filter(p -> !memorized.contains(p)).collect(Collectors.toList());

            final List<Path> decremental =
                    memorized.stream().filter(p -> !latest.contains(p)).collect(Collectors.toList());

            totalSize += incremental.stream().mapToLong(p -> p.toFile().length()).sum();
            if (decremental.size() == memorized.size()) {
                totalSize = 0;
            } else {
                totalSize -= decremental.stream().mapToLong(p -> p.toFile().length()).sum();
            }

            memorized = latest;
            return totalSize;
        }
    }
}
